Brake



E. G. CARROLL BRAKE Filed May 23, 1932 3 Sheets-Sheet 1 INVENTOR. fuss/vs- Q CAR/e 01.1.

Filed May 25, 1932 E. G. CARROLL BRAKE 3 Sheets-Sheet 2 Z V v 1v I46 [7542 80 I6 /44 7 45 W0 l I26 INVENTOR.

v foes/v:- G. C4220 ATTORNEY 0a. 20, 1936. E G CARROLL A 2,057,707

BRAKE Filed May 23, 1932 3 Sheets-Sheet 5 -36 l m g 7 286 a; I 284 I 5 p /270 Y INVENTOR.

) 6 fuss/vb G. (n/22 0L1. BY V2 ,6

' ATTORNEY,

Patented Oct. 20, 1936 UNITED STATES PATENT OFFICE BRAKE Application May 23, 1932, Serial No. 613,104

10 Claims. (01. 188-152) This application relates to braking systems and is illustrated as applied to a hydraulic brake systerm.

In some respects the invention disclosed herein is similar to the invention disclosed in the copending application of Roy S. Sanford and Eugene G. Carroll, Serial No. 609,716, but in many respects differs therefrom.

One of the objects of this invention is to provide additional safety means to guard against loss of the brakes which might occur in the event of the breaking of a spring or in the event of the failure of the vacuum.

A further object of the invention is the combination vacuum power operation and compressed air power operation for brakes.

A further object'of the invention is the combination of an air pressure system and a hydraulic pressure system for operating brakes.

One of the features of the invention is a master cylinder equipped with a hydraulic power multiplying device and combined with means for supplying additional quantities of liquid and for supplying-additional power for applying the shoes of the brakes to the drums thereof.

Further objects and features of the invention will be apparent after a reading of the subjoined specification and claims and after a consideration of the accompanying drawings in which:

Figure 1 is a diagrammatic view illustrating an automobile equipped with a braking system constructed according to my invention;

Figure 2 is a view of the combined liquid resv ervoir, vacuum booster, and compressed air booster shown in Figure 1;

Figure 3 is a view in section of a master cylinder shown in Figure 1;

Figure 4 is a sectional view showing the valve 64 of Figure 3 on a larger scale; and

Figures 5 and 6 are views corresponding generally to Figure 1 showing modified arrangements.

Referring in detail to the drawings, I have illustrated in Figure 1 an automobile provided with front wheels such as l2, with rear wheels such as M, with brakes for said wheels such as it and i8, and with means for operatingthe brakes. The means for operating the brakes include wheel cylinders and 22, conduits 24 and 26. and a master cylinder 28. e

The master cylinder 28 is shown more clearly in Figure 3 and comprises casting 30 and 32, the latter being formed with an opening 34 connected with the conduits 24 and 26. The casting 80 is formed with openings 36 and 38 for purposes later to be more fully described. Secured in the cylinder between the casting 30 and 32 is an annular head 39 provided with an annular packing cup 40 for cooperating with the front end of a plunger 42. Rearwardly thereof the casting 30 is formed with a flange 44 provided with an anl5 nular cup packing 4B which cooperates with a plunger 48.

The plunger 42 is positioned centrally of the cylinder and is formed at its forward end with a circular cross section adapted to fit loosely with- 10 in the head 39 and tightly within the cup 40. At its rearward end it is formed with a head or piston 50 which is also of circular cross section but which has a larger diameter than the plunger 42 so that it fits within the bore of the casting 30. 15 Associated with the head 50 is an annular cup packing 52 which faces rearwardly of the cylinder. The plunger 42 is formed rearwardly of the head 50 with a central projecting stem 54 adapted in the normal position of the parts of 20 the cylinder to contact with the piston 48. The plunger 48 has a circular cross section fitting within the flange 44 and within the packing 4B.

Adjacent the forward end of the plunger 42, the walls thereof are formed with one or more ports such as 56 through which liquid may flow to the portions of the system ahead of said plunger to compensate for expansion and contraction of the liquid due to temperature changes. Similarly the piston 48 adjacent to its forward end is formed with one or more ports such as 58. The rear end of the piston 48 is provided with a pair of reversed sealing cups 6!) and 82 to prevent leakage of liquid from the cylinder and to prevent the entrance of air into the cylinder. The front end of the cylinder is provided with a two-way check valve 84 normally maintained upon its seat by a spring 68, the valve allowing substantially free forward movement of the liquid and the valve and spring cooperating to maintain a slight super-atmospheric pressure in the conduits 26 and 24 and in the wheel cylinders 20 and 22. The valve 64 is described in detail and claimed in my copending application Serial Number 602,- 328. A spring 68 is interposed between the cups 46 and 52 for maintaining the cups in their operatlve positions.

Means are provided for supplying liquid to the openings 38 in the master cylinder and different means are provided for supplying liquid to the opening 38 in the master cylinder. These means include (see Fig. l) a booster 10, an air compressor 12, an air compression tank 14, the engine manifold 18, and conduits connecting these elements. The booster I0 is connected to the open- 2 ing 38.by means of a conduit 18, and is connected to the opening 36 by means of a conduit 80. The booster is connected to the manifold 16 by means of a conduit 82 and with the compressed air tank 14 by means of a conduit 84. The compressed air tank is connected to the compressor by means of a conduit 86 and is also provided with an air receiving fitting 85 such as are usually used for filling automobile tires.

' The manifold'16is adapted to draw air from the booster I0 to force liquid into the master cylinder to apply the shoes to the brakes and to apply. sufiicient'pressure to exert a small decelerating force upon the vehicle (e. g. deceleration of 5-7 ftbper second per second). The compressedair is adapted to force fluid to the master cylinder under sufllcient pressure to accomplish any desired degree of braking. A pressure relief valve 85 is interposed in the conduit 88 and asuction relief valve 81 is interposed in the conduit 82. Electric means'areprovided for controlling the suction of air from the booster I0 by the manifold I6. Interposed in the conduit 82 is a. solenoid controlled three-way valve 88,

the solenoid being operated through either one of two electric circuits. The first of the circuits may include the electric wire 82 connected to the solenoid of valve 88, the switch 94, the wire- 98, the battery I08, the wire I00, the wire I02, and the wire 80 connected to the opposite post of the solenoid. The secondcircuit includes the wire 92,, the wire I03, the double contact switch I04, the wire I 06, the battery I08, the wire I00, the wire I02, and the wire 90. The switch 94 is controlled through a spring I I0 by a foot pedal H2 so that the initial movement of thepedal closes the switch. The pedal is mechanically connected through a piston rod H4 with th piston 48. a v

The switch I04 is controlled through a foot button H6 which is (like the pedal H2) positioned convenient for operation by the driver of the vehicle. The switch I04 also controls an electric circuit formed by the wire I06 connected to the switch, the battery I08, the wire I00, the wire" H8, the solenoid of a solenoid controlled valve I20, and the wire I22 connected at one end to the solenoid and at the other end to the switch I04. The solenoid controlled three-way valve I20 is interposed in the conduit 84 and thus the button H6 is adapted not only tocontrol the vacuum power operation of the booster but. also the air pressure power operation thereof.

The booster 10 comprises a main casting I24, a lower cap casting I28 secured to said casting I24, a cylindrical can I28, and an upper cap casting I 80. Slidably mounted in the booster I0 is a liquid plunger I32 to which there is secured an'air piston I40. The air piston I40 acts (by reason of the suction of the vacuum beneath the piston and/or by reason of the pressure created above the piston by the air pressure system) to vforce the plunger I32 downward through the booster. "The piston. thusforces fluid to the master cylinder through the conduit I8 which is secured to the lower end of'the cap I 28 Air pressure is introduced through the conduit 84 which issecured in an opening in the cap member I30 and acts upon the liquid in the system. to force the liquid through the conduit 80 which. is secured to an opening in the side of the castingtI24. The air pressure also acts on the piston I40 to aid in forcing the plunger I32 downward to force liquid out through the conduit I8. Se-

cured within the casting I24 are a pair of annular heads I42 and I44. These heads are equipped with cup packings I46 and I48 respectively and together with the packings serve to seal the liquid and air systems to prevent the passage'of either liquid or air upward past the heads.

As shown in'Figure 5 I may dispense entirely with'manual operation of the brakes. In Figure 5 the parts are designated by the same numerals as are corresponding parts shown in Figure 1 with the addition of 200 to each. Therein thebooster 210 is utilized to perform the functions of a master cylinder. The conduit 218 leading from the booster is connected directly to the conduits 224 and 226. The entire hydraulic system is normally under atmospheric pressure by reason of thefact that the chamber in the cap of the booster 210 (corresponding to the cap I26 shown in Figure 2) is in communication with the interior of the plunger of the .booster 210 (which corresponds to the plunger I32 shown in Figure 2) through; ports (corresponding to the ports. I50 and I52 of Figure 2) formed in said plunger and through grooves (corresponding to grooves I54 and I56 of Figure 2) formed in the head of the booster 210 (corresponding to the head I44 of Figure 2). As soon as the vacuum means or the compressed air means is actuated, the plunger of the booster 210 (corresponding to the plunger I32 of Figure 2) forces liquid to the brakes.

If the operator desires to apply braking force manually, he depresses the pedal H2. During the first portion of the movement this action closes the switch 84 and thus operates the solenoid controlled valve 88 to shut the opening therein leading to the atmosphere and to conmeet the manifold with the booster. This causes a withdrawal of air from beneath the piston I40, and atmospheric pressure within the conduit 84 and above the piston I40 forces that piston and the plunger I82 downward. This forces liquid through the conduit 78 into themaster cylinder through the opening 38 and forces the piston 42 forward thus creating sufiicient pressure in the lines toapply the shoes to the drums. If desired, the size of the piston in the booster I0 maybe such that this result will be always just accomplished and the vacuum will not aid in the actual braking. However, I prefer to provide suflicient vacuum power to accomplish a deceleration of about 5 ft. per second per second. Further depression of the pedal II 2 will act through the liquid trapped between the pistons 48 and 42 to develop higher pressures if they are needed. By reason of the differences in areas of the piston 48 and the head of the plunger 42, the power transmitted from the pedal II 2 through the piston rod H4 is multi-' cylinder between the annular head 39 and'the plunger 50 will back up into the reservoir formed by the hollow plunger I82 and will not interfere with the operation of the device. v

When the valve I 20 is opened, the pressure of the air from the tank I4 acts both on the liquid in the interior of the plunger I32 (the plunger reservoir) and on the piston I40. The area of the piston I40 is many times the area of the liquid acted on and the area of the plunger I32. There fore, the pressure developed by said plunger on the liquid in cap I26, conduit I8 and in the space between the piston 48 and the piston 50 is many times greater than that between the piston 50 and the head 39. The force acting to move the piston 42 forward is the difference between the pressure developed in the liquid in the cap I26 by the action of the plunger I32 and that developed in the interior of the plunger I32 (the plunger reservoir) by the compressed air.

Should an emergency-stop be necessary; should the operator feel that (even though the manual power required is relatively small due to the hydraulic booster) the manual power required to operate the brake'entirely by the pedal H2 is more than he desires to exert; instead of operating the pedal I I2 the operator touches the button II6. This not only operates the valve 88, but also operates the valve I20. Thus at the same time the air beneath the piston I40 is withdrawn and additional air under pressure is supplied to the booster above the piston I40. This forces a large quantity of fluid under relatively high pressure through the conduits 18 and and thence through the conduits 24 and 26, and thus applies the brakes entirely by power with relatively high the manifold with the booster 210. This connec-.

tion causes a withdrawal of air from beneath the piston in said booster corresponding to the piston I40 and atmospheric pressure forces that piston and the plunger associated therewith downward. The downward movement forces liquid through the conduit 218 and the conduits 224 and 226 to apply the shoes to the drums. The arrangement is preferably such as to provide sufficient power to accomplish a deceleration of about five feet per second per second. If further braking is required the operator touches the button 3 I 6. This operates the valve 320. Thus additional air under pressure is supplied to the booster 210 above the piston corresponding to the piston I40 and this forces a large quantity of fluid under relatively high pressure through the conduits 218, 224 and 226 and applies the brakes entirely by power with high pressures. When a high pressure stop is required, the operator need not depress the pedal 3I2 at all inasmuch as operation of the button 3I6 will operate the valve 238 as well as the valve 320 and thus thebrakes may be applied entirely by power with relatively high pressure through the use of the button 3I6 alone.

Should it happen that the air pressure system and the vacuum system of the vehicle should both fail at the same time, nevertheless the brakes may be operated directly through the pedal II2. Under such circumstances the piston rod I [4 acts through the piston 48 and the extension 54 to slightly larger area than the area of pistons usually used (the forward end of the plunger 42 and the forward end of the plunger 48 preferably having a diameter of 1 inches), the pressure required for this emergency operation would be higher than that normally required in the operation of hydraulic brakes, but the pressure re quired would not be excessive nor objectionable in such unusual operations.

Due to the fact that an air pressure in the tank 14 of about 30 lbs. will be sufficient to provide adequate brakes, a very cheap compressor I2 may be used and even if desired the compressor I2 may be eliminated, the tank 14 being periodically station.

The use of compressed air eliminates the lag in the operation of the brakes which might at times be objectionable in a vacuum system if used alone.

As shown in Figure 6 I may enlarge the reservoir tank 414 and provide a, partition 415. The tank is thus provided with an air pressure portion 483 to which is connected the conduits 434 and 486 and with a vacuum portion 48I which is interposed in the conduit 482 between the valves 481 and 488. In this figure all other parts corresponding to parts of Figure l are designated by the same numerals with the addition of 400.

It is to be understood that the above described embodiment of my invention is for the purpose of illustration only, and various changes may be made therein without departing from the spirit and scope of the invention. v

I claim:

1. In a braking system for actuating wheel brakes, a master cylinder, means for forcing fluid from said cylinder for actuating,said brakes comprising a forward piston positioned in said cylinder axially thereof, a rearward piston positioned in said cylinder axially thereof disconnected from said forward piston, and power means for forcing fluid to said cylinder.

2. In a braking system. a master cylinder, a forward piston positioned therein. a rearward pis ton positioned therein, said pistons contacting with each other in their normal inoperative positions, and being at times spaced from each other whereby at such times force acting upon said rearward piston in a forward direction is transmitted through interposed fluid to the forward between said two pistons, whereby at such times force acting on said rearward piston in a forward direction is transmitted through the fluid to the forward piston, and power means forforcing fluid into said cylinder.

4. In a. braking system, a master cylinder, a forwardpiston positioned therein, a rearward piston positioned therein at times spaced from said forward piston, means for trapping fluid between said two pistons, whereby at such times force acting on said rearward piston in a forward direction is transmitted through the fluid to the forward piston and pneumatically operated power means for operating one of said pistons.

5. In a. braking system, a master cylinder, a forward piston positioned therein, a rearward piston positioned therein at times spaced from force acting on said said forward piston,

means for trapping fluid between said two pistons, whereby at such times rearward piston in a forward direction is transmitted through the fluid to the forward piston, and vacuum .operated power means for forcing fluid into said cylinder.

6. In a braking system, a master cylinder, a forward piston positioned therein, a rearward piston positioned therein at times spaced from said. forward piston, means for trapping fluid betweensaid two pistons, wherebyat such times force acting on said rearward piston in a forward direction is transmitted through the fluid separately and successively a greater pressure to said liquid. I Y

9. In a fluid braking system, a container for liquid, power means for applying a vlimited amount of pressure tosaid liquid, additional power means for applying a greater pressure to said liquid, electrically controlled means for actuating said first named power means only, and additional electrically controlled means capable of actuating both of said power means.

10. In a fluid transmitting system, a master positioned therein, a rearward cylinder having an opening adjacent to the forward end thereof, an opening in the side inter-' mediate its ends, and an opening in the side adjacent to the rear thereof; sealing means for preventing fluid entering through said rear opening from passing rearwardly therefrom; a rear annular head positioned just in advance of said rear opening; sealing means associated with said head for at times preventing passage of fluid rearwardly thereby but always allowing substantially free forward'passage of fluid; a. forward annular head positioned intermediate between said intermediate opening and said forward opening; sealing means associated with said last:

named head for at times preventing passage offluid rearwardly thereby but always allowing substantially'free forward passage of fluid; a forward plunger having a relatively small forward piston passing through said forward head, fitting in the opening therein, formed with a port to allow passage of fluid normally past said forward head in both directions and having arelatively large rearward piston positioned to move between said rear head and said intermediate opening; a sealing means associated with said rearwardpiston for preventing passage of fluid forwardly thereby; a rear plunger having a, relatively small diameter, passing through, said rearward head, fitting in the opening therein, and formed with a port to allow passage of fluid normally past said rearward head in both directions; means for supplying fluid under atmospheric pressure to said intermediate opening; and means for supplying fluid under superatmospheric pressure to said rearward opening.

EUGENE G. CARROLL. 

